Patient Reported Outcomes

The Importance of Self-Reporting

Why do we need self-reporting?

Human behaviour is a complex and dynamic process that is affected by a multitude of external influences, internal factors and emotions. Researchers, scientists and clinicians are often concerned with the real-world behaviour of subjects but rarely have the means at their disposal to elicit such accurate, fine-grained behavioural data. The CamNtech PRO-Diary provides a convenient solution for data collection.

Self-reporting provides a relatively simple means of obtaining data directly from the patient by methods such as questionnaires, interviews or diaries. Large amounts of information can be collected at low cost and low patient burden. These Patient Reported Outcomes (PROs) and Patient Reported Outcomes Measures (PROMs) are a valuable supplement to objectively measured data. PRO endpoints are often required to effectively evaluate the treatment benefit provided by new medical products (e.g., drugs) in clinical trials.

What are PROs and PROMs?

Patient-Reported Outcomes (PROs) are defined by the National Quality Forum as “any report of the status of a patient’s health condition that comes directly from the patient, without interpretation of the patient’s response by a clinician or anyone else.”

Patient Reported Outcome Measures (PROMs) are the mechanisms used to measure PROs. These will typically be in the form of self-reporting via standardised, validated questionnaires and can be classified as either generic or disease specific. The generic tools measure diverse aspects of a broad range of medical conditions, allowing for the overall evaluation of care, quality of life, and cost effectiveness of interventions. The disease specific PROMs allow individual aspects of a condition and their impact on outcome to be examined.

Ecological Momentary Assessment (EMA)

Human behaviour is typically monitored by means of global or retrospective self-reporting, for example ‘how much pain did you experience in a day?’ or ‘how active were you yesterday?’. This approach does not consider the dynamic nature of human behaviour and how it is affected by complex factors such as mood, interactions with others and with their environment.

Ecological Momentary Assessment (EMA) aims to address the limitations of retrospective self-reporting by sampling behaviour at regular intervals to build a true picture over time and avoids recall bias by asking the question ‘in the moment’.

EMA involves repeated sampling of subjects’ current behaviours and experiences in real time, in subjects’ natural environments. EMA aims to minimize recall bias, maximize ecological validity, and allow study of micro processes that influence behaviour in real world contexts.

EMA has been extensively used to study phenomena as diverse as daily variation in mood and tiredness, fatigue, pain, eating, smoking and alcohol behaviours.


Methods used for collecting PRO data

There are several limitations depending upon the method chosen to collect self-report data and we will examine some of the common methods with their associated weaknesses below.


Paper Diaries or Questionnaires

The most common method of collecting PRO is the paper diary. They are attractive to researchers because of the low initial outlay and are perceived as being easy for subjects to understand and easy to complete. However, the validity of the data collected by the paper method has been repeatedly called in to question with very poor patient compliance levels. One key problem is ‘hoarding’ where the patient either forgets to complete the questionnaire or defers completion until necessary. The resulting data suffers from recall bias and gaps as the patient attempts to remember the answers from hours or days before. In one study conducted by Stone et al. the compliance with paper diaries was found to be as low as 11% vs compliance of 94% with electronic diaries. As the sampling is under the control of the patient, paper diaries are not well suited to EMA. The low start-up cost is often cited as an advantage of paper diaries however, this is misleading as the on-going management costs for collection and transposition can escalate the total project costs rapidly, particularly in larger scale projects.


One alternative to paper based PRO is to interview the patient, either by phone or in person. Although the costs are obviously higher, the traditional perception has been that it produces both better quality data and higher response rates. However there are potential problems associated with administering interviews:  if interviewers need to be hired and trained it will add significantly to the overall costs of the study. It is not a proactive method of recording data, e.g. if the subject is experiencing pain they must wait until the interview to report the level of discomfort hence introducing possible recall bias and other limitations on non EMA sampling. Additionally, there may be concerns over answering ‘sensitive’ questions due to embarrassment, cultural difference or social desirability bias resulting in the over-reporting of desirable behaviours, and under-reporting of undesirable behaviours.

Online Questionnaires

Like the paper diary this online questionnaires have similar advantages in terms of low administration cost and with fewer drawbacks when it comes to collation because the data is already in an electronic format. Evidence suggests that Web-based versions of tests may not always measure the same constructs as their paper predecessors. Ultimately many have found that, like paper diaries, non-compliance is a serious cause for concern with some finding that response rates to online questionnaires were lower than paper questionnaires. As the sampling is under the control of the patient, online questionnaires are not well suited to EMA.


Electronic PROs (e-PRO) are the increasingly popular method of collecting patient data and have been key to the growth of EMA. The movement from paper-based to e-PRO data collection has enhanced the integrity and accuracy of PRO data in clinical trials. The US Food and Drug Administration has made it clear that electronic capture of clinical trial source data is preferred over paper-based data collection.

Tablets are a commonly used solution for e-PRO but require the patient to have access to the device at the appropriate times for completing the questionnaires. The US FDA has also indicated that a common platform should be used across a study meaning that an identical device type would need to be supplied to all participants. A similar approach is to use smartphones which are more easily carried by the patient but have the same limitations regarding platform commonality. A typical solution is to provide all subjects with the hardware pre-configured with the questionnaire software or App to complete the study. Tablets and smartphones tend to have relatively short battery life and are also quite vulnerable to damage through accidental drops. Furthermore, it is imperative to ‘lock down’ such devices to prevent unauthorised apps or usage that may interfere with the questionnaires or may compromise data security. This may mean that patient would have to carry their own smartphone in addition to the study phone which would be less than convenient.

CamNtech PRO-Diary

The PRO-Diary offers a unique e-PRO solution that combines a wrist-worn electronic patient diary with an accelerometer allowing the simultaneous collection of subjective and objective patient data.

The PRO–Diary user interface consists of a touch sensitive ‘slider’, two touch sensitive buttons and an ultra–clear OLED screen. The subject is then prompted by audible (or optionally vibratory) alerts according to the programmed schedule. The PRO-Diary is a key tool for the collection of EMA data as the user is prompted to answer on your pre-defined schedule. As the device is wrist-worn, it is more difficult to ignore the prompts and missed prompts are logged.

Click or tap here for more information…

  Key Benefits

Subjective and Objective data

Sleep and Activity Data

Ecological Momentary Assessment

High compliance vs paper diary

Up to 4 weeks battery life

Multiple question types

Flexible questionnaires

Scheduled or on demand alerts

Open data format

Touch sensitive controls

Clear, bright OLED display

The PRO-Diary system offers full flexibility to create your own questions and arrange the questions into questionnaires. The PRO-Diary has eight basic question types which may be configured using the PRO-Diary software.

The PRO-Diary accelerometer data may be analysed using our comprehensive MotionWare software for endpoints such as sleep quality, circadian rhythm and physical activity levels.

The PRO-Diary has been used in multiple EMA studies. Click or tap here to view scientific publications.

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UK & International customers

CamNtech Ltd.
Manor Farm
PE28 9JD, UK

US customers

CamNtech Inc.
630 Boerne Stage Airfield,
Texas 78006,


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